This invention generally relates to a method for forming containers from a thermoplastic material. More particularly, this invention is concerned with a plastic bottle forming method which uses a neck holding device to transfer the bottle from station to station in a multi-step forming process, particularly in the final blowing of a biaxially oriented article.
The use of more than one station in the forming of plastic bottles is known in the art. It is always desired to improve the forming process whenever possible. One area where improvement is desired is in the formation of the finish portion. Examples of prior art processes may be seen in U.S. Pat. No. 3,767,747, now U.S. Pat. No. Re. 29,065, and U.S. Pat. No. 3,978,184 as well as the article "Stretch Blow Molding PVC and Nitriles," Modern Plastics, pp 32-86, September, 1976, the teachings of all of which are hereby incorporated by reference. Yet another prior art system may be seen in U.S. Pat. No. 4,004,872. We have developed a process that uses neckrings or neck clamps to transfer a plastic container through various stages of formation as opposed to using a mold or blow pin as taught by the prior art, thus achieving better accuracy in finish formation.